In electronic book voice reproduction systems in which the reproduction speed is adjusted, users are required to switch the voice reproduction speed manually and cumbersome manipulations are necessary. Also, users tend to merely hear a reproduction voice monotonously without remembering much of its contents.
One countermeasure against the above is a restrictive system in which the reproduction speed of educational content data which contains difficulty information is controlled (see JP-A-2008-96482, for instance). This is a network learning assist system in which the voice reproduction speed is determined dynamically based on difficulty in a particular interval of video-audio data and proficiency level of a learner.
However, it is desired to provide a technique for controlling the voice reproduction speed that is more suitable for general use.